Whereas Part 1 of this three-part installment covered connections to and power sources for fire pumps (August 2024), and Part 2 dealt with disconnecting means, overcurrent protection, and transformers (October 2024), the final part of this series will address supply conductors, general wiring, and fire pump redundancy.
There are two categories of power supply conductors covered in Art. 695. The first is service conductors, which are conductors ahead of the fire pump disconnecting means on the electric utility source service. The second is feeder conductors, which are conductors on the load side of the fire pump disconnecting means or conductors that connect to an on-site generator. There are different requirements for each of these conditions, which you can find under Sec. 695.6(A) [Supply Conductors]. Here is what the Code says about service conductors.
“(1) Services and On-Site Power Production Facilities. Service conductors and conductors supplied by on-site power production facilities shall be physically routed outside a building(s) and shall be installed as service-entrance conductors in accordance with Sec. 230.6, Sec. 230.9, and Parts III and IV of Art. 230. Where supply conductors cannot be physically routed outside of buildings, the conductors shall be permitted to be routed through the building(s) where installed in accordance with 230.6(1) or (2).”
In the Figure below, the service conductors are labeled “Utility Service Lateral Conductors” or “Fire Pump Service Conductors.” Routing these conductors outside the building is easily accomplished if the main electrical room is at ground level, and the building is slab-on-grade construction with no basement levels. In this scenario, the conductors would be routed underground beneath the ground floor slab, which is considered outside the building per Sec. 230.6(1). It is more difficult to meet this requirement in a building with a basement level and the main electrical room is either in the basement or at the ground level. In my experience with electrical inspectors, they allow the service conductors to be routed exposed within the main electrical room if installed in rigid steel conduit. This is due to the Code allowance for an exception under the feeder conductors below, when located in the electrical room where they originate, to not require the minimum 2-hour fire separation or fire-resistance rating within the same room.
If both the feeder conductors and the service conductors are in the same room, why would one requirement be more stringent than the other? This should be reviewed and signed off with your local electrical inspector before application. The alternative is to encase these conduits in concrete within the main electrical room, which would be difficult to achieve if suspended from the structure above.
The feeder conductors have several more options for routing within a building.
“(2) Feeders. Fire pump supply conductors on the load side of the final disconnecting means and overcurrent device(s) permitted by 695.4(B), or conductors that connect directly to an on-site standby generator, shall comply with all of the following:
(1) Independent Routing. The conductors shall be kept entirely independent of all other wiring.
(2) Associated Fire Pump Loads. The conductors shall supply only loads that are directly associated with the fire pump system.
(3) Protection from Potential Damage. The conductors shall be protected from potential damage by fire, structural failure, or operational accident.
(4) Inside of a Building. Where routed through a building, the conductors shall be protected from fire for 2 hours using one of the following methods:
a. The cable or raceway is encased in a minimum of 50 mm (2 in.) of concrete.
b. The cable or raceway is a listed fire-resistive cable system.
c. The cable or raceway is a listed electrical circuit protective system.
“Informational Note No. 1: Electrical circuit protective systems could include, but are not limited to, thermal barriers or a protective shaft and are tested in accordance with UL 1724, Fire Tests for Electrical Circuit Protection Systems.
“Exception to 695.6(a)(2)(4): The supply conductors located in the electrical equipment room where they originate and in the fire pump room shall not be required to have the minimum 2-hour fire separation or fire-resistance rating unless otherwise required by 700.10(D) of this Code.”
The first thing to note is that the above applies to both the electric utility source and the standby generator source. The routing is independent of other electrical wiring in the building and cannot serve anything but associated fire pump loads. Where the feeder conductors are routed inside the building, they can either be concrete encased, a listed fire-resistive cable, or a listed electrical circuit protective system, which includes a 2-hour rated shaft construction of sheetrock and studs. The Code provides an exception to this requirement for feeder conductors routed within the main electrical room where the feeder originates and within the fire pump room. Outside of these rooms, if the feeder conductors cannot be routed underground, then one of the above methods would apply.
The supply conductors serving fire and jockey pump loads shall be sized no less than 125% of the sum of combined motor full-load current and 100% of any other associated fire pump accessory equipment. For fire pump-only load, the conductors shall be sized per Sec. 430.22.
Where the fire pump is a tapped service, the Tap Rule of Sec. 240.21 shall not apply because it relates to overload protection. The fire pump controller and ATS, if provided, shall not serve any other loads but the fire pump. Ground-fault protection shall not be provided on any fire pump circuits.
Voltage drop
When starting, the voltage on the line side terminals of the fire pump controller shall not drop more than 15%. This requirement is outlined in Sec. 695.7 [Voltage Drop].
“(A) Starting. The voltage at the fire pump controller line terminals shall not drop more than 15 percent below normal (controller-rated voltage) under motor starting conditions.”
While running, the voltage on the load side terminals of the fire pump controller shall not drop more than 5% when the motor is operating at 115% of full load.
“(B) Running. The voltage at the load terminals of the fire pump controller shall not drop more than 5 percent below the voltage rating of the motor connected to those terminals when the motor is operating at 115 percent of the full-load current rating of the motor.”
Control wiring
Most of the control wiring required for the fire pump operation does not fall under the electrical contractor’s scope of work. The control wiring between the fire pump controller's transfer switch and the standby generator does. These requirements are as follows:
“NEC 695.14(F) Generator Control Wiring Methods. Control conductors installed between the fire pump power transfer switch and the standby generator supplying the fire pump during normal power loss shall be kept entirely independent of all other wiring. The integrity of the generator remote start circuit shall be monitored for broken, disconnected, or shorted wires. Loss of integrity shall start the generator(s).
“The control conductors shall be protected to resist potential damage by fire or structural failure. Where routed through a building, the conductors shall be protected from fire for 2 hours using one of the following methods:
“(1) The cable or raceway is encased in a minimum of 50 mm (2 in.) of concrete.
“(2) The cable or raceway is a listed fire-resistive cable system.
“(3) The cable or raceway is protected by a listed electrical circuit protective system.”
The preferred method would be to route the control wiring underground beneath the slab-on-grade, putting it outside the building. If not possible, the above aligns with the requirements for the feeder conductor routing, so the same would apply here. This Section does not include the exception that alleviates the requirement when routed within the fire pump room and the electrical room of origin. I assume that this was inadvertent, and the exception was meant to be included.
Miscellaneous
There is nothing specific addressing multiple fire pump installations in Art. 695. However, in each of the Code Sections addressed above, the reference to fire pump is made in the plural form [i.e., pump(s)]. The implication is that it not only applies to a single pump installation but also to multiple pump installations. It does not require duplication of what is installed for service to one fire pump at a second fire pump location. Assuming the service is sized appropriately to accommodate both pumps, it allows the installation of one fire pump to service the second fire pump.
For redundancy purposes, multiple fire pumps are required in high-rise construction when buildings are taller than 200 feet per the California Building Code (CBC), Chapter 4.
“403.3.2.1 Fire Pumps. Redundant fire pump systems shall be required for high-rise buildings having an occupied floor more than 200 feet above the lowest level of fire department vehicle access. Each fire pump system shall be capable of automatically supplying the required demand for automatic sprinkler and standpipe systems.”
Redundant fire pumps are treated the same as primary fire pumps for both the power service and fire alarm monitoring. The only difference is the building service does not need to be sized to accommodate both pumps for simultaneous operation, as only one pump can operate at a time.
For even taller buildings, there may be a requirement for more than one primary fire pump to meet the pressure requirements on the upper floors. In this scenario, the primary pumps could operate simultaneously, requiring the service to be sized appropriately. However, each primary pump will require a redundant pump, and these pumps will not operate simultaneously with their associated primary pumps.
In the following application, there is a primary pump and a redundant pump, and both do not operate simultaneously. If the primary pump fails for any reason, the redundant pump starts and takes over. The Figure is a diagram of how these pumps should be connected, assuming a 12kV service to the building. There are occasions when additional primary pumps are required to maintain pressure in even taller buildings.
Note there is a single tap for both fire pumps, a single overcurrent protection device, and a single transformer for the electric utility service. All of these are sized for a single motor, as both will not operate simultaneously. There are two non-fused disconnect switches (one for each fire pump) on the secondary side of the transformer. These are there for maintenance purposes only, allowing one fire pump to be disconnected without affecting the operation of the other. If there are no disconnects on the secondary side, the primary disconnect would need to be opened for work on the pump controller, making the generator the only source of power for the other fire pump. This arrangement has been accepted in the San Francisco Bay Area but should be verified with local inspectors elsewhere.
On the generator side, there are two overcurrent disconnect devices — one for each fire pump. Since these devices are sized for the normal operation of a motor, they will trip in an overcurrent or overheating scenario, so the failure of one pump does not disable the operation of the other pump.
There are occasions when additional primary pumps are required to maintain pressure in very tall buildings. For each of the primary pumps, there will be the need for a redundant pump. The example in the Figure above would just grow to accommodate.
Conclusion
Hopefully, this three-part series provided you with a better understanding of electric-driven fire pumps and the interface with the electrical systems within a building. I know it is a topic of some controversy with many differing opinions, but my goal was to address the issue from a Code perspective and provide a simple solution.
**Reproduced with edits and permission of NFPA from NFPA 70*, National Electrical Code, 2017 edition. Copyright© 2016, National Fire Protection Association. For a full copy of the NFPA 70, please go to www.nfpa.org.
